Rolling process plays an important role in the manufacture of Bi-based high temperature superconductor tapes, and the plastic flow regularities of the superconducting wires during deformation will directly affect the ...Rolling process plays an important role in the manufacture of Bi-based high temperature superconductor tapes, and the plastic flow regularities of the superconducting wires during deformation will directly affect the ultimate quality of the tapes. In order to investigate the effect of cross-sectional shapes before fiat rolling on the performance and homogeneity of the tapes, some numerical models of Bi-2223/Ag wires with different cross-sectional shapes including circular, square, elliptical and racetrack cross-sections are constructed during the rolling process. By comparing the relative density, logarithmic strain ratio and length-width ratio on the filaments, it is revealed that Bi-2223/Ag wire with special-shaped cross-section can achieve better conductivity than the round wire, in particular, the racetrack cross-sectional wire has the second best performance among four wires. Based on material processability and experimental condition, tri-pass racetrack drawing technique is employed to optimize the process and obtain racetrack cross-sectional wire. The rolling process of Bi-2223/Ag wire with racetrack cross-section causes more intensive deformation of filaments in the center of the tape and achieves the filaments with larger length-width ratio. Also, the deformation distribution of filaments verifies the numerical results. Consequently, the racetrack drawing technique can be utilized for a reference during the mechanical processing and to increase the current transmission capacities of Bi-2223/Ag tapes.展开更多
The 3D viscous incompressible magneto-hydrodynamic (MHD) system comprised by the 3D incompressible viscous Navier-Stokes equation couples with Maxwell equation.The global well-posedness of the coupled system is still ...The 3D viscous incompressible magneto-hydrodynamic (MHD) system comprised by the 3D incompressible viscous Navier-Stokes equation couples with Maxwell equation.The global well-posedness of the coupled system is still an open problem.In this paper,we study the Cauchy problem of this coupled system and establish some logarithmical type of blow-up criterion for smooth solution in Lorentz spaces.展开更多
The traditional rolling process of Bi-2223/Ag wires with circular sections is an inhomogeneous process. For the purpose of achieving a uniform filaments distribution, a novel technique for round wire through racetrack...The traditional rolling process of Bi-2223/Ag wires with circular sections is an inhomogeneous process. For the purpose of achieving a uniform filaments distribution, a novel technique for round wire through racetrack-type dies during the last several passes of drawing is necessarily brought forward. In order to investigate the processing behaviors of superconducting filaments, a numerical model for the three passes of racetrack drawing was constructed, and subsequently, the optimization of three racetrack-type dies was designed based on the simulation results. Then the three passes of racetrack drawing was applied to fabricate Bi-2223/Ag tape and the density distribution of each filament of the wire was studied by Vickers microhardness. The experimental results showed that the racetrack drawing can obtain dense superconducting filaments, and improve the mechanical properties and critical current of the final tape.展开更多
this paper,we study a class of sublinear operators and their commutators with a weighted BMO function.We first give the definition of a weighted Morrey space Lpo(X)where X is an RD-measure and w is the weight function...this paper,we study a class of sublinear operators and their commutators with a weighted BMO function.We first give the definition of a weighted Morrey space Lpo(X)where X is an RD-measure and w is the weight function.The weighted Morrey spaces arise from studying the local behavior of solutions to certain partial differential equations.We will show that the aforementioned class of operators and their communtators with a weighted BMO function are bounded in the weighted Morrey space LPpto(X)provided that the weight function w belongs to the Ap(μ)-class and satisfiesthereverseHolder'scondition.展开更多
基金supported by Major Program of National Natural Science Foundation of China (Grant No. 50635050)National Natural Science Foundation of China (Grant No. 50575124)
文摘Rolling process plays an important role in the manufacture of Bi-based high temperature superconductor tapes, and the plastic flow regularities of the superconducting wires during deformation will directly affect the ultimate quality of the tapes. In order to investigate the effect of cross-sectional shapes before fiat rolling on the performance and homogeneity of the tapes, some numerical models of Bi-2223/Ag wires with different cross-sectional shapes including circular, square, elliptical and racetrack cross-sections are constructed during the rolling process. By comparing the relative density, logarithmic strain ratio and length-width ratio on the filaments, it is revealed that Bi-2223/Ag wire with special-shaped cross-section can achieve better conductivity than the round wire, in particular, the racetrack cross-sectional wire has the second best performance among four wires. Based on material processability and experimental condition, tri-pass racetrack drawing technique is employed to optimize the process and obtain racetrack cross-sectional wire. The rolling process of Bi-2223/Ag wire with racetrack cross-section causes more intensive deformation of filaments in the center of the tape and achieves the filaments with larger length-width ratio. Also, the deformation distribution of filaments verifies the numerical results. Consequently, the racetrack drawing technique can be utilized for a reference during the mechanical processing and to increase the current transmission capacities of Bi-2223/Ag tapes.
基金Xin-Guang Yang was partially supported by the Fund of Young Backbone Teacher in Henan Province(No.2018GGJS039)Yongjin Lu is partially supported by NSF(Award No:1601127).
文摘The 3D viscous incompressible magneto-hydrodynamic (MHD) system comprised by the 3D incompressible viscous Navier-Stokes equation couples with Maxwell equation.The global well-posedness of the coupled system is still an open problem.In this paper,we study the Cauchy problem of this coupled system and establish some logarithmical type of blow-up criterion for smooth solution in Lorentz spaces.
基金Supported by the National Natural Science Foundation of China (Grant No. 50635050)
文摘The traditional rolling process of Bi-2223/Ag wires with circular sections is an inhomogeneous process. For the purpose of achieving a uniform filaments distribution, a novel technique for round wire through racetrack-type dies during the last several passes of drawing is necessarily brought forward. In order to investigate the processing behaviors of superconducting filaments, a numerical model for the three passes of racetrack drawing was constructed, and subsequently, the optimization of three racetrack-type dies was designed based on the simulation results. Then the three passes of racetrack drawing was applied to fabricate Bi-2223/Ag tape and the density distribution of each filament of the wire was studied by Vickers microhardness. The experimental results showed that the racetrack drawing can obtain dense superconducting filaments, and improve the mechanical properties and critical current of the final tape.
文摘this paper,we study a class of sublinear operators and their commutators with a weighted BMO function.We first give the definition of a weighted Morrey space Lpo(X)where X is an RD-measure and w is the weight function.The weighted Morrey spaces arise from studying the local behavior of solutions to certain partial differential equations.We will show that the aforementioned class of operators and their communtators with a weighted BMO function are bounded in the weighted Morrey space LPpto(X)provided that the weight function w belongs to the Ap(μ)-class and satisfiesthereverseHolder'scondition.
